An Overview of Dermatomyositis

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Dermatomyositis is a rare inflammatory disease that primarily affects the skin and muscles (myopathy) but may also affect other organs of the body. Research suggests that dermatomyositis is an autoimmune disorder in which the body attacks its own healthy cells. The defining symptom is a skin rash that develops or appears at the same time as muscle weakness. While it can occur in people of any age, dermatomyositis typically affects adults in their late 40s to early 60s and is more prevalent among women than men. In children, the onset of juvenile dermatomyositis takes place between 5 and 15. While there's no known cure for dermatomyositis, symptoms can be treated.

Symptoms

Symptoms of dermatomyositis, one of only three known inflammatory myopathies, can develop gradually over weeks or months or come on suddenly. They include:

  • A reddish-purple to dusky-red rash, called a heliotrope rash, in a symmetrical distribution around the eyes
  • Dark red bumps, called Gottron papules, or raised blotches on the knuckles, finger or toe joints, elbows, ankles, or knees
  • Hard, irregular-shaped lumps, called calcinosis, in or on the knuckles, finger or toe joints, elbows, ankles, or knees. This occurs mostly in children, though 20% of adults with dermatomyositis also have calcinosis.
  • Sudden or progressive weakness in muscles in the neck, hips, back, thighs, and shoulders, which can occur on both sides of the body
  • A scaly scalp or diffuse hair loss
  • Difficulty swallowing (dysphagia) or a feeling of choking
  • Fatigue or muscle weakness when climbing stairs, rising from a sitting position, or lifting the arms
  • In adults, dermatomyositis may also be accompanied by weight loss, a low-grade fever, inflamed lungs, and sensitivity to light
  • Unintentional weight loss
  • Fever

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Dermatomyositis on face
Dermatomyositis on face. DermNet / CC BY-NC-ND

The muscle weakness and rash associated with dermatomyositis can also lead to other complications, such as skin and gastric ulcers, and malnutrition.

Although it's relatively uncommon, some people with dermatomyositis experience systemic symptoms such as arthritis. Adults over 60 with the condition sometimes have a higher risk of developing cancer.

Finally, in some instances dermatomyositis is associated with the following conditions:

  • Myocarditis
  • Raynaud’s phenomenon
  • Interstitial lung disease
  • Connective tissue diseases

Causes

The primary cause of dermatomyositis is not known. Some theories suggest that it's an autoimmune reaction and associated with conditions like lupus or a viral infection of the skeletal muscle disease. There may also be a genetic component to the condition, although it's not classified as a genetic disorder. It sometimes occurs in people who have cancer of the abdomen, lungs, or other parts of the body.

Diagnosis

In someone with dermatomyositis, tell-tale skin symptoms—rash, papules, and calcinosis nodules—often show up first.

Since these can sometimes be mistaken for symptoms of lupus erythematosus, psoriasis, or lichen planus, a doctor is unlikely to rely only on a physical exam to diagnose dermatomyositis. Other diagnostics include:

  • Blood tests that detect muscle enzymes and markers of inflammation (Some people with dermatomyositis test positive for an antinuclear antibody (ANA) blood test)
  • Magnetic resonance imaging (MRI) and electromyography (EMG)
  • Muscle biopsy to help assess muscle damage and inflammation
  • Blood analysis to check levels of muscle enzymes and autoantibodies, which are antibodies that attack normal cells

Treatment

Treatment for dermatomyositis includes relieving muscle weakness and skin symptoms. A corticosteroid such as Prednisone can ease muscle inflammation. If the side effects of steroids become severe, immunosuppressant or cytotoxic medications, such as Rheumatrex (methotrexate) or Imuran (azathioprine) may be used. Rheumatrex can also help reduce skin symptoms.

Physical and occupational therapy can help improve muscle function and prevent complications such as contractures, which is a shortening and hardening of muscles or tendons.

People with dermatomyositis are photosensitive and should protect their skin from sun exposure.

Some people with dermatomyositis require treatment for systemic symptoms or complications. In children and adolescents, calcinosis can complicate treatment.

Symptoms may resolve completely after a course of corticosteroids. This remission may last a long time or, in some cases, be permanent.

A Word From Verywell

Corticosteroids, especially in high doses, shouldn’t be used for extended periods of time to treat dermatomyositis because of their potential side effects. Your doctor will most likely start you on a high dose, then gradually lower it. Some people can eventually stop taking corticosteroids completely if their symptoms disappear for a prolonged period of time after stopping the medication.

If corticosteroids alone don’t improve symptoms, your doctor may prescribe other medications to suppress your immune system.

Most people with dermatomyositis require long-term treatment. And while some people develop cancer or organ failure, which can affect life expectancy, many individuals respond well to treatment and have relief of most, if not all, symptoms.

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